Moisture and other contaminants continue to pose problems for recovered fiber end-users, a group of paper mill production managers said at a panel discussion at the 2005 Paper Recycling Conference & Trade Show held June 26-28 in Atlanta.
Terry Bliss with Process Consultants Inc. moderated the session titled “The Loose, the Baled and the Ugly,” with panelists John Davis from Sonoco Products Co., and Mary-Kay Lynde-Maas of SP Newsprint Co.
“Recycled paper is a ‘semi-perishable’ material,” said Bliss.
In indoor or covered storage, bale moisture can reach anywhere from 12 to 20 percent, Bliss said. Outside, with rain exposure, that number can increase to 50 percent.
According to Bliss, increased moisture content not only leads to a significant loss in fiber strength, it can attract bio-pests like molds and insects.
High moisture content can also lead to a decrease in brightness—an important quality issue for high grades, Bliss said. If newsprint yellows, end-users will pay significantly more in expensive chemical treatments to restore brightness, he added.
Bliss said that the trend toward single stream recycling has had a negative impact on fiber quality by introducing more moisture and contaminants to fiber. Higher moisture content can result from collecting and transporting paper in open bins or trucks.
Bio-pests and pathogens can threaten the safety of workers in addition to diminishing the quality of the product, said Lynde-Maas. While any pathogens would most likely be destroyed during the paper-making process and pose little threat to consumers of the end product, mill workers could be exposed to them at any stage, she said.
To reduce variations in moisture content, Bliss said many mills try to mix truckloads on the conveyor. Some mix bales from different vendors and even keep a reserve of material known to be of good quality on hand. However, Bliss pointed out that even these traditional fixes have problems—loads are not always effectively mixed themselves and reserved bales can be stored for long periods of time, subjecting them to all the problems associated with long-term storage.
Davis agreed that the overall quality of recovered paper has been on the decline and increasing contamination has been leading to increasing costs for mills. Davis says prohibitives like metal, glass, plastic and wax are finding their way into bales in increasing amounts, in many cases in light of the growing popularity of single-stream recycling. The growing shredding industry is also challenging paper mills by making contaminants smaller and more difficult to remove, Davis said.
Contaminants do more than pose threats to workers and decrease product quality, Davis said. They also lead to excessive wear on processing equipment, driving up costs to mills with more frequent maintenance.
“The best thing we can do is get contamination out as soon as possible,” he said. He recommended better communication between suppliers and end users as a good starting point for combating declining quality, as well as better use of technology.